.backtotop{
    position:fixed;
    right: 80px;
    bottom: 88px;
    width: 28px;
    height: 46px;
    /* border: 1px solid #000; */
    background: url(../images/backtop.png) no-repeat 0 0;
}
.backtop:hover {
    background-position: -38px 0;
}